We should sign players that look good in similar system than ours. Meaning useless pressing, not enough workrate, not enough tactical discipline etc. If a defender look good somewhere else in a team like this sign him up.
But sign up Bonucci who looked very good in a Juve side that was created by a clever manager and played by the system working really hard with lot of effort and discipline with Vidal, Marchisio,Pogba etc and immense track back from wide players then bring him here to put in a side that just doesnt work hard off the ball thats madness...
Simeone knows a few things about defending well, and he is happy to play our Stefan Savic in CB. Sign him up and play him in our system and he will look worse than he looked under Mancini.
Sign him up with Godin who is a fantastic CB and they are a duo at Atletico, and they wont be much better than Kolarov-Stones duo. Which means in a different system I am sure even Kolarov and Stones and otamendi would look much much better defenders.
Or just remember Lescott's best years for us, the system we played in that times, the clean sheets we had.
And then imagine Lescott playing at the half way line with Vardy, Hazard running at him with no protection from midfield.